Pre-Heater For An Apparatus For The Production Of Carbon Black

ABSTRACT

A pre-heater for an apparatus for the production of carbon black, is adapted to pre-heat air by heat exchange to a temperature of at least 800° C., comprises an elongated jacket arranged substantially and having a top end and a bottom end, said jacket defining a space, a plurality of tubings arranged inside said space, said tubings having a diameter of 85 to 90 mm, said jacket being provided with an air inlet and an air outlet, for allowing said air to enter and exit said space, a smoke inlet chamber and a smoke collection chamber for allowing smoke to enter and exit said tubing. Said jacket is supported by a suspension means between said top and bottom ends excluding at the top end as such, such that the jacket is allowed to expand upwards above and downwards below said suspension means.

TECHNICAL FIELD

The present invention relates to a pre-heater for an apparatus for theproduction of carbon black, wherein air to be pre-heated by combustionfumes are adapted to increase the temperature of the air by heatexchange to a temperature of at least 800° C., comprising an elongatedjacket adapted to be arranged substantially vertically and having a topend and a bottom end, said jacket defining a space, a plurality oftubings arranged inside said space, said tubings having a diameter of 85to 90 mm, said jacket being provided with an air inlet and an airoutlet, for allowing said air to enter and exit said space, a smokeinlet chamber and a smoke collection chamber for allowing smoke to enterand exit said tubings.

The invention also relates to an apparatus for the production of carbonblack, comprising a burner connected to a fuel or gas source, to afeedstock source and to a combustion reactor, said combustion reactorbeing connected to said smoke inlet chamber, and a fan delivering air tosuch a pre-heater.

Such a pre-heater and such an apparatus for the production of carbonblack are known from the prior art discussion of EP-B-0 865 600, FIGS. 1and 2. The known pre-heater is however disadvantageous, since it isself-supporting on a bottom flange, causing high compressive stresses inthe lower part of the shell of the pre-heater. The same relates to thepre-heater of WO 98/54529.

FR-C-892 762 discloses a heat exchanger having a jacket with verticaltubings inside, The heat exchanger tubings are suspended in the top endthereof for preventing high compressive stresses in the tubings.

It is generally known to suspend a pre-heater in springs at the top endthereof. However, that kind of suspension cannot absorb horizontalloads, due to heavy wind or earth quakes.

EP-A-0 246 488 discloses a combustion cooler suspended by support meanson the mantle. However, the heal exchanger thereof is neither intendedfor, nor possible to be used at high temperatures.

DISCLOSURE OF THE INVENTION

One object of the present invention is to improve the mechanicalstability of the jacket of the pre-heater.

This has been solved by a pre-heater of the initially defined kind,wherein said jacket is supported by a suspension means between said topend and said bottom end, excluding at the top end as such, such that thejacket is allowed to expand upwards above said suspension means anddownwards below said suspension means.

Hereby, the jacket of the pre-heater will be exposed to less compressivestress, i.e. mechanical instability, such as buckling, is prevented. Asa consequence of this, longer pre-heaters can be used, and thus highertemperatures can be allowed in the pre-heater.

Furthermore, “flag pulling”, i.e. bending of the pre-heater caused byuneven thermal expansion of the jacket, due to plugging of tubes oruneven flow distribution can be absorbed.

Furthermore, the pre-heater external forces, such as wind and earthquake loads will be absorbed via the suspension means.

Preferably, said suspension means is arranged above the centre ofgravity of the pre-heater. In addition or alternatively, said suspensionmeans is arranged at the upper half of the elongation of the jacket. Inparticular said suspension means is arranged substantially a third ofthe elongation of the jacket from said top end. Hereby is achieved anoptimal balance between the centre of gravity and/or the length of thejacket and a desired downward expansion of the pre-heater below thesuspension means.

Suitably said air inlet is arranged substantially at said top end, saidair outlet being arranged substantially at said bottom end, said airbeing pressurised and conveyed from said air inlet to said air outletexterior of said tubings.

Preferably, said smoke inlet chamber is arranged substantially at saidbottom end, said smoke collection chamber being arranged substantiallyat said top end, wherein said tubings are adapted to convey smoke fromsaid smoke inlet chamber to said smoke collection chamber.

Hereby, a counter flow heat exchange is achieved, wherein the hot gasesenter in the bottom of the pre-heater and exit at its top, whereas theair enter in the top and exits at the bottom thereof.

Advantageously, an expansion compensator is arranged at said bottom end.Hereby, the downward directed expansion of the pre-heater is absorbed.

Preferably, said expansion compensator defines at least a part of saidsmoke collection chamber, Hereby, a gas tight flexible connection isachieved.

Suitably, said expansion compensator comprises a bellows. Alternatively,a pack box may be utilised.

In particular, said bellows Is metallic and is protected by a refractorylining. Hereby, the metallic bellows Is protected from hot processgases. Alternatively a fabric bellows may be utilised.

Preferably, said suspension means is adapted to be connected to asupport means of a supporting structure in such a way that thesuspension means is substantially prevented from performing movements.

Preferably, a lower portion of the pre-heater is provided with a guidingmeans adapted for guiding the pre-heater to move in a substantiallyvertical direction. Hereby, the pre-heater is guided in a controlledmanner during expansion.

Suitably, the length of said tubings is within the range of 12 to 20metres. Hereby, the pre-heater is adapted to produce combustion air,i.e. air to be supplied to the burner, in a temperature range of about800-1000° C.

More particular, If the length of said tubings is within the range of 12to 13 metres, the pre-heater is adapted produce combustion air at atemperature of about 800° C.; while a length of said tubings within therange of 14 to 16 metres increases the temperature of the combustion airto about 900° C.; while a length of said tubings within the range of 17to 20 metres, increases the temperature of the combustion air to about 1000° C. Of course, the temperature does not increase in steps.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in further detail withreference to the accompanying drawings, according to which

FIG. 1 illustrates schematically an apparatus for the production ofcarbon black with a pre-heater according to the invention:

FIG. 2 a is a horizontal cross-section along lines II-II of thepre-heater shown in FIG. 1;

FIG. 2 b is a tube sheet for the pre-heater shown in FIG. 1.

FIG. 3 is an enlargement of the expansion compensator shown in FIG. 1;

FIGS. 4 a and 4 b illustrate the expansion compensator in differentpositions; and

FIGS. 5A-5C illustrate the position of a suspension means.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows an apparatus 2 for the production of carbon black,comprising a fan 4 for supply of pressurised air via a pipe 6 to an airinlet 3 of a jacket 10 of a pre-heater 12. The pre-heated air is furtherdistributed through an outlet 13 via a pipe 14 to a burner 16. Theburner 16 is furthermore supplied with fuel or gas via a tube 18 andcarbon black feedstock, such as thick oil or tar via a tubing 19. Theburner is connected to a carbon black reactor 20, in turn connected to aconnection part 21, where the fumes created In the reactor rise via anexpansion compensator 22 to tubings 23, sealingly connected at theiropposite ends, respectively to openings of a tube plate 23 a (cf. FIG. 2b). The connection part 21 and the expansion compensator 22 thustogether constitute a smoke collection chamber 24. The tube plates 23prevent the exhausts from entering the space between the tubings.

The reactor is furthermore provided with water nozzles 25 for stoppingthe combustion reaction and for cooling the fumes.

The pre-heater 12 is intended for increasing the efficiency of theprocess in the carbon black reactor 22. The higher the reachedtemperature of the air in the pre-heater 12, the higher the efficiency.However, the higher the temperature In the pre-heater, the more thestrength of the material thereof will be affected. An increase of thetemperature requires a larger heat exchanging surface, i.e. either alonger or wider pre-heater, in any case resulting in a heavyconstruction. In turn, this adds to weakening of the material, inparticular of the jacket.

The outer diameter of the tubings used in pre-heaters for the productionof carbon black are generally 85-90 mm. Most commonly, an outer diameterof substantially 89 mm is utilised, in particular 88.9 mm. A largerdiameter would cause problems with the strength of material of the tubesheets 23 a, while tubings of a smaller diameter than 85 mm would causeproblems with clogging carbon black.

When using tubings having a diameter of 85-90 mm and a length of 12 to13 metres, a temperature of the combustion air of about 800° C. isobtainable, while with tubings being 14-16 metres, a temperature of thecombustion air of about 900° C., and with tubings having a length of17-20 metres a temperature of the combustion air of about 1000° C. isobtainable.

In order to compensate for the decrease of the strength of the materialof the pre-heater, the jacket is suspended by a suspension means 28,which will be further described in further detail below.

The smoke led through the tubings 23 are collected in a top cone 27 adefining a smoke collection chamber 27 b.

The fumes are led through a pipe 28 to a heat exchanger 30, that coolsthe fumes e.g. by means of oil or water and further via a tube 32 to afiltering device 34 for collecting the carbon black produced in thereactor 20, and the purified fumes are transported via a not shown plantfor further purification of the fumes to a chimney 40.

In FIG. 2 a is shown a horizontal cross-section along the line IIa-IIaof the pre-heater shown in FIG. 1. The suspension means 26 comprisesfour radially extending brackets 42 arranged on the jacket 10. Thebrackets 42 are supported by a support device 44 comprising four I-barsforming a square, arranged on a not shown support structure.

Of course, more or less than four brackets may be used and more or lessthan four I-bars may be used, Furthermore, other kinds of bars thanI-bars may be utilised. Furthermore, an annular bracket about thecircumference of the jacket 12 may be used.

It should be contemplated that the suspension means 20 may be flexibleand/or elastic, comprising e.g. compressible or tensile springs,compressible pads or the like. It should however be noted that thesuspension means is substantially prevented from movement by the supportdevice 44 and the support structure.

In FIG. 3, the expansion compensator 22 is shown in further detail. Anupper flange 46 is adapted to be connected to the Jacket 10 of thepre-heater 12, whereas a lower flange 48 is adapted to be connected tothe connection part 21. The upper flange 48 is connected to an innersleeve 50 whereas the lower flange 48 is connected to an outer sleeve52.

A heat resisting ring 54 is arranged on said inner sleeve 50. A metallicbellows 56 is arranged between the upper and lower flanges 46, 48. Theinner sleeve 50 is slidingly arranged in relation to an outer sleeve 62.

FIGS. 4A and 4B illustrate how the inner and outer sleeves, 50, 52constitute a labyrinth sealing 55 protecting the metallic bellows 56from the hot process gases. A horizontal guiding means 58, comprising atleast one protection member 60 and at least one guide member 62, isprovided for guiding the jacket 10, such that horizontal movements ofthe lower end of the jacket 10 are prevented, in turn protecting thebellows 56 from performing substantially other than axial movements.

In FIG. 5A is shown how the support means 28 is arranged at differentpositions above half the longitudinal extension of the jacket. Theoptimal position has proven to be at ⅓ from the top of the jacket.

In FIGS. 5B and 5C are shown how the support means is arranged above thecentre of gravity of the pre-heater. In cases where the centre ofgravity is very low, the position of the support means may even be underhalf the longitudinal extension of the jacket.

Operation

During operation, the air from the fan 4 will be pre-heated outside thetubings 23 in the space inside the jacket 10. The pre-heated air is ledin the pipe 14 to the burner 16. The more the air is pre-heated the moreefficient the carbon black reaction will be, and in turn the lower theenergy consumption, i.e. the pre-heater increases the efficiency of theprocess. In order to produce carbon black, the reaction is performed atimperfect combustion, i.e. at under-stoicheiometric combustion.

The hot gases produced In the carbon black reactor 20 are led throughthe smoke collection chamber through the pre-heater 12. The hot gaseswill cause expansion of the pre-heater 12. The suspension means 28causes the part of the pre-heater above the suspension means 26 toexpand upwards, whereas the part of the pre-heater underneath thesuspension means 26 will expand downwards. Consequently, the part of thepre-heater underneath the suspension means 26 will not be subjected tocompressive forces.

The downward expansion is further controlled by the guiding means 58.

1: A pre-heater for an apparatus for the production of carbon black,wherein air to be pre-heated by combustion fumes are adapted to increasethe temperature of the air by heat exchange to a temperature of at least800° C., comprising an elongated jacket adapted to be arrangedsubstantially vertically and having a top end and a bottom end, saidjacket defining a space, a plurality of tubings arranged inside saidspace, said tubings having a diameter of 85 to 90 mm, said jacket beingprovided with an air inlet and an air outlet, for allowing said air toenter and exit said space, a smoke inlet chamber and a smoke collectionchamber for allowing smoke to enter and exit said tubings, wherein saidjacket is supported by a suspension means between said top end and saidbottom end, excluding at the top end as such, such that the jacket isallowed to expand upwards above said suspension means and downwardsbelow said suspension means, wherein said suspension means is arrangedabove the centre of gravity of the pre-heater and/or said suspensionmeans being arranged at the upper half of the elongation of the jacket.2: A pre-heater according to claim 1, wherein said suspension means isarranged substantially a third of the elongation of the jacket from saidtop end. 3: A pre-heater according to claim 1, wherein said air inlet isarranged substantially at said top end, said air outlet being arrangedsubstantially at said bottom end, said air being pressurised andconveyed from said air inlet to said air outlet exterior of saidtubings. 4: A pre-heater according to claim 1, wherein said smoke inletchamber is arranged substantially at said bottom end, said smokecollection chamber being arranged substantially at said top end, whereinsaid tubings are adapted to convey smoke from said smoke inlet chamberto said smoke collection chamber. 5: A pre-heater according to claim 1,wherein an expansion compensator is arranged at said bottom end. 6: Apre-heater according to claim 5, wherein said expansion compensatordefines at least a part of said smoke collection chamber. 7: Apre-heater according to claim 5, wherein said expansion compensatorcomprises a bellows. 8: A pre-heater according to claim 7, wherein saidbellows is metallic and is protected by a refractory lining. 9: Apre-heater according to claim 7, wherein said suspension means isadapted to be connected to a support means of a supporting structure insuch a way that the suspension means is substantially prevented fromperforming movements. 10: A pre-heater according to claim 1, wherein alower portion of the pre-heater is provided with a guiding means adaptedfor guiding the pre-heater to move in a substantially verticaldirection. 11: A pre-heater according claim 1, wherein the length ofsaid tubings is within the range of 12 to 20 meters, respectively. 12: Apre-heater according to claim 11, wherein the length of said tubingsrange of 12-13 meters, respectively. 13: A pre-heater according to claim11, wherein the length of said tubings is within the range of 14-16meters, respectively. 14: A pre-heater according to claim 11, whereinthe length of said tubings is within the range of 17-20 meters,respectively. 15: A pre-heater according to claim 1, wherein the outerdiameter of the tubings is substantially 89 mm. 16: A pre-heateraccording to claim 1, wherein the outer diameter of the tubings is 88.9mm. 17: An apparatus for the production of carbon black, comprising aburner connected to a fuel or gas source, to a feedstock source and to acombustion reactor, said combustion reactor being connected to saidsmoke inlet chamber, and a fan, characterized in that wherein the fan isadapted to deliver air to a pre-heater according to claim 1 any one ofthe preceding claims, said air outlet being connected to said burner.